Oslo: A Norwegian military transport plane with five people aboard went missing Thursday during an exercise and was feared to have crashed in bad weather in a mountainous area in northern Sweden, officials said.

The C-130 was heading from Evenes, on Norway`s Arctic coast, to the Swedish city of Kiruna when it disappeared from radar screens just before 3 p.m. (1400 GMT), rescue coordinators said.

"We have to assume that we are looking for a plane that has crashed," Norwegian military spokesman John Espen Lien said.

A military helicopter searching the area picked up an emergency signal near mount Kebnekaise, 80 kilometers (50 miles) west of Kiruna, Swedish air rescue spokesman Jonas Sundin said.

"They thought they heard a weak signal," he said, adding rescuers were trying to pinpoint the location of the signal but were hampered by cloud cover and poor visibility due to strong winds whipping up snow.

All five on board were Norwegians, officials said.

Rescue services from Sweden and Norway, as well as military helicopters and fighter jets taking part in the exercise, were involved in the search, Swedish air rescue coordinator Birgitta Eckermark said.

She said that the crew`s last contact with the Kiruna control tower was at 2:43 p.m. and the plane dropped off the radar 13 minutes later.

Norwegian military spokeswoman Marianne Oeiahals said Norwegian and Swedish soldiers were also entering the area on foot.

The plane went missing while on route to Kiruna to pick up personnel during a winter exercise called Cold Response, with 16,000 soldiers from 14 countries taking part.

The purpose of the Norwegian-led exercise "is to rehearse high intensity operations in winter conditions within NATO with a UN mandate," the country`s military said.